The present invention relates to an apparatus and method of measuring one or more downhole conditions in a well bore, particularly, a battery-powered, positive-pulse-telemetry system for directional survey and steering applications.
In rotary drilling operations, it is very common to measure one or more downhole conditions as drilling progresses. Consequently, various types of directional drilling systems have been developed. Typically, these systems are of the mud-pulse telemetry type for transmitting measurement data to receiving equipment located on the surface. For example, it is quite common to check the inclination and orientation of a well bore. Inclination is the deviation of the well bore from a vertical direction. Orientation refers to the relative rotation of the tool with respect to a selected side of the tool. In addition, it is very common to check the azimuthal direction of the well bore as drilling progresses. Inclination or drift typically has a range of 0 to 90.0 degrees maximum, while tool face orientation and azimuth both have a maximum range of 360.0 degrees.
These variables are measured, encoded and transmitted to the surface via the mud stream. This is accomplished by modulating the mud pressure and sensing the resultant mud pulses at the surface. Various pressure transducers are available for detecting pressure variations in the mud flow at the surface.
It is, therefore, an object of the present invention to provide an improved measuring while drilling system incorporating a battery-powered, positive-pulse-telemetry system.